1. Field of the Invention
The present invention relates to an image recording apparatus suitably used for a copying or facsimile machine for recording image information on a recording medium.
2. Related Background Art
A typical example of an apparatus of this type is a so-called dual mode copying machine in which information such as date and characters input from a host computer or the like is recorded by a sub-record optical system while an original is copied by a main record optical system. The sub-record optical system may comprise a laser having a larger output quantity of light than that of an LED (Light-Emitting Diode) to erase an unnecessary portion of an image, in addition to image recording.
When a laser is used as a sub-record optical system, it is generally employed to adjust a value of a current supplied to the laser by properly controlling a time interval of a laser, because an optical output (light quantity) changes as a function of temperature. A typical conventional adjustment method is performed as follows. A sensor is arranged to monitor an optical output from the laser, and the laser is then deenergized. Thereafter, a current is gradually increased until a sensor output reaches a predetermined value.
When such a conventional control method is employed, the optical output is temporarily erased (OFF), an unnecessary black image is formed in background scanning; that is, in the case where the portion irradiated with a laser beam is recorded in white, for example.
When a laser is used in a sub-record optical system to erase an unnecessary image portion at the start of recording, copying cannot be started until a polygonal mirror for laser scanning is rotated and reaches a steady speed. In addition, the ON time of the laser is prolonged to shorten the mechanical service time of the apparatus, thus degrading reliability of the apparatus.
In multifunctioning of an image recording apparatus such as a copying machine in recent years, functions such as a variable magnification function, an automatic density adjustment function, an automatic paper size selection function, an automatic magnification selection function, a multicolor copying function, an automatic both side recording function, an image editing function, a two-color development function accessible with an operation of one button, a page consecutive copying function, and a binding margin adjustment function have been, available. At present, combinations of these functions are also required.
In such a conventional apparatus described above, it is expected to easily emphasize image information.
Examples of an apparatus for recording an image on a common recording medium by using a plurality of light sources are described in U.S. Pat. Nos. 4,552,449, 4,434,982, 4,378,156, and U.S. Pat. No. 4,517,579, and U.S. Ser. No. 839,358 (Aug. 5, 1986) now abandoned. There is much room left for further improvements.